Language
In Chinese dictionaries, aside from being indexed by Pinyin, characters are also indexed by radicals. A radical is a common set of strokes shared by many characters. A Chinese character is often made up by a radical and another character. A radical can be a character on its own.
Looking Up a Character
A radical has certain number of strokes. To look up a word, we have to first find the number of strokes of the radical; then find out the number of strokes of the remaining character; then look under the category where the stroke number matches the number of the strokes of the remaining character to find the one we are looking for. For example, the character, , has a radical that has 2 strokes,, and the remaining character has 3 strokes,. So, to find this word, we look up for a two-stroke radical. Then we look under the three-stroke characters to find the character we are looking for.
Radical Chart
The above graphic courtesy of NJStar.com.

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